Broke my dogs flea collar

I took my dog out to use the bathroom today. in the process, her normal collar slipped off. so I went tried to grab her flea collar so she wouldn’t run into the street. The flea collar ended up breaking. When i tired to put it on I realized I couldn’t get it as tight as it was before but it’s still on just more loose than before. Is the flea collar still affective or do I need to buy another one?